Threaded fastening devices or so-called Tee-nuts are widely used in the furniture industry for securing components of furniture together. Such nuts are formed of sheet metal, and incorporate a threaded sleeve or barrel, and an integral face flange, and spikes, which are embedded in the workpiece around a pre-drilled hole. They are used, for example, in the construction of beds, for securing legs to a bed frame, and other furniture items.
Various forms of apparatus have been devised for the power-operated setting of such fastening devices at a high rate of speed. One example of such a fastener setting apparatus is shown in U.S. Pat. No. 3,460,217.
The apparatus disclosed in that patent has operated satisfactorily for many years. In that apparatus, the wooden workpiece was first of all placed on a lower working surface. Tee-nuts were fed from a hopper down a curved ramp, to a power-operated setting plunger located above the workpiece. The tee-nut was held in registration with the bottom of the plunger, and when the plunger was operated downwardly the tee-nut was released, and the plunger struck the tee-nut forcing it downwardly into a hole in the workpiece. This principle of operation involved certain problems in design. For example, it was necessary to time the plunger stroke carefully. As a result, considerable care had to be exercised in the manufacture, and adjustment of the apparatus. If this was not achieved, then either the nut would fall before the plunger could catch up with it, or alternatively the plunger would strike the nut too soon before it was released.
Another problem in the design of such earlier machines was that they required the use of a hopper, and a relatively expensive feed mechanism, for feeding the loose nuts. These requirements added to the complexity and hence the expense of such earlier apparatus. These factors had, in turn, limited the scope of the sales of such machines. In practice, they were economical only for relatively large scale manufacturing facilities.
A further proposal is shown in U.S. Pat. No. 4,821,940, granted to Allan C. Rotherham entitled T-nut Insertion Machine.
In this machine, a hopper and feed mechanism generally similar to that shown in earlier T-nut insertion machines, was used. However, in this machine, the T-nuts were fed to a feed mechanism from which they were delivered one at a time to a plunger. The plunger in this case operated with an upward insertion stroke, so that the T-nut was forced upwardly into the workpiece.
Above the workpiece, a stationary anvil or support was located against which the workpiece was held, while the T-nut was forced upwardly. In this device, however, the T-nuts were simply placed loose in the hopper as in the earlier devices, and as a result, it was necessary to provide for a two position delivery system for delivering the T-nuts to the plunger.
The T-nuts were thus delivered to a preliminary insertion location, at which point they stopped. The endmost T-nut was then moved over a ledge, one at a time, from the preliminary location, to the so called extended location, in which position it was then held ready for insertion by the plunger.
Clearly, if a machine could be designed at a much lower cost and, in particular, without the use of an expensive and complex hopper and feed mechanism, then the sales of such a machine could be made on a much larger scale, to a much greater range of customers.
Preferably, such a machine will operate on the method of upward insertion of fasteners, into a work-piece from below the work-piece, by moving each fastener upwardly, so as to produce significant advantages over earlier systems.
Preferably also, the invention will provide for a new and unique package of such fasteners arranged in a strip, for easy handling, and positioning in such an apparatus.